Problem: Ashley is 5 times as old as Daniel and is also 40 years older than Daniel. How old is Daniel?
We can use the given information to write down two equations that describe the ages of Ashley and Daniel. Let Ashley's current age be $a$ and Daniel's current age be $d$ $a = 5d$ $a = d + 40$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $d$ , and both of our equations have $a$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $5d$ $-$ $ (d + 40)$ which combines the information about $d$ from both of our original equations. Solving for $d$ , we get: $4 d = 40$ $d = 10$.